1Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB T6G 2P5, Canada2Department of Animal Biosciences, University of Guelph, Guelph, ON N1G 2W1, Canada

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Abstract

Body weight (BW) and rearing photoperiod are important factors affecting sexual maturation rate and reproductive performance in broiler breeders. The current experiment used a 2 × 3 factorial arrangement of treatments to study the interaction between BW and rearing photoperiod on reproductive performance in group housed broiler breeder hens, while minimizing variation in BW. Hens (n = 180) were fed with a precision feeding system to allocate feed individually to achieve the breeder-recommended target curve (Standard) or to a target curve that reached the 21 wk BW at 18 wk (High). Hens were on 8L:16D, 10L:14D, or 12L:12D photoschedules during rearing and were photostimulated at 21 wk with a 16L:8D photoschedule. Sexual maturity (defined as age at first egg) and individual egg production to 55 wk were recorded. At 55 wk, proportional weights of individual body components were determined by dissection. Differences were reported as significant at P ≤ 0.05. A significant interaction between BW and rearing photoschedule affected age at sexual maturity and egg production. In the High BW treatment, age at sexual maturity did not differ between hens under the 8L:16D and 10L:14D photoschedules (173 vs. 172 d, respectively). In the Standard BW treatment, the 12L:12D rearing photoperiod delayed sexual maturity compared with the 8L:16D rearing photoperiod (266 vs. 180 d, respectively). All hens on the High BW treatment laid at least 1 egg before the end of the experiment. Conversely, 3.3, 18.1, and 37.6% of Standard BW hens on the 8L:16D, 10L:14D, and 12L:12D photoschedules, respectively, never commenced egg production. At the end of the experiment, proportional breast weight was higher and proportional fatpad weight was lower in Standard compared to High BW hens (25.8 vs. 27.5% and 2.4 vs. 1.5% of BW, respectively). We conclude that increased BW partially counters the effect of longer photoschedules on sexual maturity in broiler breeders and that dissipation of the photorefractory state depends on BW.